If I had to guess, I think the depiction of the Sandler's had something to do with it. In the skit, the on-screen text for the Sandler's read:
I don't think the Sandler's, who are private citizens, would think being labeled "should be shot" was very funny, and I can see that their lawyer may assert that it goes beyond the bounds of satire or parody. Ad Age magazine has asked for an explanation from NBC, but NBC has not returned their calls.